KeshanAmare
The Dark Shadow
In all honesty, Naruto needs to end after this arc. There really isn't much Kishi can do after what he's doing in this arc and there's no way for him to top the current power levels. Not to mention introducing even stronger opponents would make no sense in the context of the story. Right now we have basically every powerful ninja in history preparing to fight it out. The only way for it to work is if Kishi just began again with all new characters. Otherwise Kishi will be jumping the shark over another shark.
Yeah...I guess. This war will end it all. So let's just wait until it happens. It's Kishi's choice.
From what we've seen, Mokuton doesn't seem like it would be weak against fire, Since Hashirama regularly went up against Katon users without any trouble and elementally it's made from part water. Kishi has already set up a way to deal with all the Zetsus: Kabuto's poison, Which controls and can probably kill Mokuton cells.
But they're still fodder.
I don't know about death fodder. We have already seen that they can take the shape and ability of any ninja they touch and merge into the ground undetected. Not to mention when they die, They could release the spores to suck out their opponent's chakra and trap them at the same time. I see them being a real threat to the alliance.
They'll probably come up with something to get rid of them. Maybe Kakashi's Mangekyou?
I would hate for the dead ninjas to come back to life. That seems like a cheap cop out and has already been done with Konoha. But if it's to be done, It probably would involve the power of the Rinnegan, Which has already been shown.
I want to know more about the Juubi, the doujutsu it has, and the Rinnegan powers which are related to Naruto.